fsdax: dax_unshare_iter() should return a valid length

The copy_mc_to_kernel() will return 0 if it executed successfully.  Then
the return value should be set to the length it copied.

[akpm@linux-foundation.org: don't mess up `ret', per Matthew]
Link: https://lkml.kernel.org/r/1675341227-14-1-git-send-email-ruansy.fnst@fujitsu.com
Fixes: d984648e428b ("fsdax,xfs: port unshare to fsdax")
Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/dax.c b/fs/dax.c
index c48a3a93ab2974785d3346bf98c59c4110be3122..3e457a16c7d1828f5a70c8c9f5dcad4a422cd2ad 100644 (file)
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1271,8 +1271,9 @@ static s64 dax_unshare_iter(struct iomap_iter *iter)
        if (ret < 0)
                goto out_unlock;
 
-       ret = copy_mc_to_kernel(daddr, saddr, length);
-       if (ret)
+       if (copy_mc_to_kernel(daddr, saddr, length) == 0)
+               ret = length;
+       else
                ret = -EIO;
 
 out_unlock: